I once heard Bob Murphy bring up this point in the application of Rom 13.

If Romans 13 means Christians should support their government, then what justification can the US have to overthrow the government in Iraq. After all, Rom 13 says they are "ministers of God".

Most that hold to Romans 13 justifying governments like the one in the US seem to be pretty flexible in its application. Its interesting to say the least.

This is an area of much disagreement and I think its healthy to wrestle with it. I have for years. Those that seem to use Romans 13 to justify the US gov don't like to talk about Nazi Germany and how it was applied by churchmen of the time that remained silent. I don't see a massive gap between Nazi Germany and Rome of Paul's day. There's a clear difference but on the authoritarian side of things Rome was pretty terrible... and yet. We have Romans 13 to deal with.